Syntheses and Structural Researches of Nine-coordinate K3[TbIII(nta)2(H2O)]·5.5H2O and Eight-coordinate K3[YbIII(nta)2]·5H2O

The crystal and molecular structures of K3[TbIII(nta)2(H2O)](5.5H2O (nta = nitrilotriacetic acid) and K3[YbIII(nta)2](5H2O complexes have been determined by single-crystal Xray structural analyses. Because TbIII and YbIII have different ionic radii and electronic configura- tions, they take nine- and eight-coordinate structures with two nta ligands, respectively. The crystal of K3[TbIII(nta)2(H2O)](5.5H2O belongs to orthorhombic, space group Pccn with a = 1.6374(7), b = 1.9913(8), c = 1.5068(6) nm, V = 4.913(3) nm3, Z = 8, Mr = 769.54, Dc = 2.081 g/cm3, μ= 3.476 mm-1 and F(000) = 3048. The final R and wR are 0.0432 and 0.0916 for 4961 observed reflections (I > 2.0(σI)), and 0.0814 and 0.1042 for all 21921 reflections, respectively. The [TbIII(nta)2(H2O)]3- complex anion has a nine-coordinate pseudo-monocapped square anti-prismatic structure, in which two N and six O coordinated atoms are from two nta ligands and the left ninth O atom from one water molecule. The crystal of K3[YbIII(nta)2]·5H2O is of monoclinic, space group P21/c with a = 1.5579(5), b = 0.9981(3), c = 1.5956(5) nm, β = 109.776(5), V = 2.3348(13) nm3, Z = 4, Mr = 756.62, Dc = 2.153 g/cm3, μ= 4.624 mm-1 and F(000) = 1484. The final R and wR are 0.0253 and 0.0657 for 4123 observed reflections (I > 2.0(σI)), and 0.0320 and 0.0731 for all 9414 reflections, respectively. The [YbIII(nta)2]3- complex anion has an eight-coordination structure with a distorted square antiprismatic prism, in which each nta acts as a tetradentate ligand with one N atom from the amino group and three O atoms from the carboxylic groups.     

Kinetic study of the protonations and substitutions of different cobalt(III)–nta complexes

The behaviour of the Cobalt(III)–nta (nta = nitrilotriacetate) system in an acidic medium was investigated. The acid dissociation constant, pK _a1, of [(nta)(H₂O)Co(-OH)Co(H₂O)(nta)]^– was determined as 3.09(3) and the pK _a of the cis-[Co(nta)(H₂O)₂]/[Co(nta)(H₂O)(OH)]^– equilibrium was determined as 6.71(1). cis-[Co(nta)(H₂O)₂] undergoes ring-opening upon acidification below pH = 2.0. The formation of [Co( ³-nta)(H₂O)₃]⁺ was also studied. The substitutions between cis-[Co(nta)(H₂O)₂] and NCS^– ions were investigated in the pH = 2–7 ranges. [Co(nta) (H₂O)(OH)]^– reacts ca. 70 times faster at 24.7 °C with NCS^– ions than cis-[Co(nta)(H₂O)₂], indicating a cis-labilising effect of the OH^– ligand.     

Syntheses and Structural Researches of Nine-coordinate K_3[Tb~Ⅲ(nta)_2(H_2O)]·5.5H_2O and Eight-coordinate K_3[Yb~Ⅲ(nta)_2]·5H_2O

1 INTRODUCTION Because the rare earth metal complexes have promoting function to the growth of animals and plants[1] and many other biological activities[2～5], such as antiinflammation, antibacterium, anticoagu- lantion and anticaner, the investigation …     

Tetracarbonyliron adducts of Cp2Cr2(CO)4(μ-η2-P2). Syntheses and crystal structures of Cp2Cr2(CO)4P2[Fe(CO)4] m (m=1 and 2)

Cp₂Cr₂(CO)₄( - ² - P₂), 1, reacts with one molar equivalent of Fe₂(CO)₉ in THF to yield the mono- and di-iron complexes, Cp₂Cr₂(CO)₄P₂[Fe(CO)₄], 2, (16.5% yield) and Cp₂Cr₂(CO)₄P₂[Fe(CO)₄]₂, 3, (16.9% yield), as dark magenta brown and dark greenish brown crystals, respectively. Both complexes were characterized by single-crystal X-ray diffraction analysis. Crystal data –2: space group =P2₁/c,a=17.024(1) Å,b=8.180(1) Å,c=30.891(2) Å, =100.953(5)°,V=4223.4(7)ų,Z=8, 3743 observed reflections,R _F=0.033; 3: space group P1,a=10.209(2) Å,b=10.212(2) Å,c=15.989(3) Å, =106.93(1)°, =91.87(1)°, =119.50(1)°,V=1356.5(4) ų,Z=2, 3489 observed reflections,R _F=0.029.     

Electrochemical reductive acylation of (η6-arene)Cr(CO)3 complexes and (benzophenone)[Cr(CO)3]2

The electrochemical reductive acylation of (benzophenone)Cr(CO)₃ and (benzophenone) [Cr(CO)₃]₂ has been performed in DMF, by electrochemical reduction of complexed ketones in the presence of acetic and benzoic anhydride in excess. Three complexed benzhydryl esters ArCH(OCOR)PhCr(CO)₃, (Ar = Ph, R = Me: Ar = PhCr(CO)₃, R = Me; Ar = PhCr(CO)₃, R = Ph) were obtained in 46–57.5% yields after purification. Electrochemical reduction of (diphenylmethane)Cr(CO)₃ in the presence of acetic anhydride in excess leads to m-benzyl acetophenone.     

Synthesis, Structure and Characterization of Two-dimensional Network Copper Complex [Cu_3(nta)_2(azpy)_2(H_2O)_2]·6H_2O

ＩｎｔｒｏｄｕｃｔｉｏｎＣｒｙｓｔａｌｅｎｇｉｎｅｅｒｉｎｇｏｆｓｕｐｒａｍｏｌｅｃｕｌａｒａｒｃｈｉｔｅｃｔｕｒｅｓｓｕｓｔａｉｎｅｄｂｙｃｏｏｒｄｉｎａｔｅｃｏｖａｌｅｎｔｂｏｎｄｓｏｒｈｙｄｒｏｇｅｎｂｏｎｄｓｒｅｐｒｅｓｅｎｔｓａｒａｐｉｄｌｙｅｘｐａｎｄｉｎｇｆｉｅｌｄｔｈａｔｏｆｆｅｒｓｐｏ ｔｅｎｔｉａｌｆｏｒｄｅｖｅｌｏｐｍｅｎｔｏｆｎｅｗｃｌａｓｓｅｓｏｆｆｕｎｃｔｉｏｎａｌｓｏｌｉｄｓ .1,2 Ｔｈｅａｒｃｈｉｔｅｃｔｕｒｅｓｏｆｃｏｏｒｄｉｎａｔｉｏｎｐｏｌｙｍｅｒｓｃａｎｂｅ…     

A kinetic study on the iron(III)-promoted aquation of [Cr(C2O4)2(picolinato)]2− and [Cr(C2O4)2(2-pyridineacetato)]2− complexes

Two [Cr(C₂O₄)₂(AB)]^2– type complexes, obtained from the reaction of cis-[Cr(C₂O₄)₂(H₂O)₂]^– with the AB ligand, [AB = picolinic (pyac) or 2-pyridine-ethanoic acid (pyeac) anions], were converted into [Cr(C₂O₄)(pyac)(H₂O)₂]⁰ and [Cr(C₂O₄)(pyeac)(H₂O)₂]⁰ compounds, respectively via Fe^III-induced substitution of the oxalato ligand. The aquation products were separated chromatographically and their spectral characteristics and acid dissociation constants determined. The kinetics of the oxalato ligand substitution were studied with a 10–40 fold excess of Fe^III over [Cr^III] at [H⁺] = 0.2 M and at constant ionic strength 1.0 M (Na⁺, H⁺, Fe³⁺, ClO^– ₄). The reaction rate law is of the form: r = k _obs[Cr^III], where k _obs = kQ[Fe^III]/(1 + Q[Fe^III]). The first-order rate constants (k), preequilibria quotients (Q) and activation parameters derived from the k values have been determined. The reaction mechanism is discussed in terms of a Lewis acid catalyzed (induced) ligand substitution.     

Syntheses and Structural Researches of Yb~(3+) Complexes with Nitrilotriacetic Acids──Nine-coordinate K_3[Yb(nta)_2(H_2O)]·5H_2O and Eight-coordinate Na_3[Yb(nta)_2]·6H_2O Complexes

IntroductionBecause the rare earth metal compounds havethe promotion to the growth of animals andplants[1] ,and the functions of antiinflammation,antibacterium[2 ] ,anticoagulantion[3 ] and anti-caner[4] ,the investigation on the syntheses and bio-logical activities of the rare earth metal compoundshas attracted many chemists attention.The com-pounds of heavy rare earth element Yb are consid-ered as the representative of these rare earth metalcompounds.Otherwise,the radioactive rare earthmetal…     

Kinetics and mechanism of base hydrolysis of mer-[Cr(pic)3]0 and [Cr(ox)2(pic)]2? (pic?=?picolinate, ox?=?oxalate)

Mer-[Cr(pic)₃]⁰ and [Cr(ox)₂(pic)]²⁻ undergo successive base hydrolysis to give chromates(III). Dissociation of the first ligand, pic from [Cr(pic)₃]⁰ and ox from [Cr(ox)₂(pic)]²⁻, proceeds in two stages, namely initial chelate-ring opening followed by slower liberation of the monodentate ligand. Kinetics of both the stages were studied spectrophotometrically in 0.2–0.9 M NaOH solution, under pseudo-first-order conditions. The calculated values of k _obs were independent of [OH⁻]. A mechanism is proposed, where the formation of intermediates in the hydroxo form prevents the monodentate ligand from undergoing chelate-ring closure. Evidence for the formation of an intermediate with O-bonded picolinate is given. The effects of pH and the complex composition on the reactivity are discussed.     

Density functional calculations of the structures and bond energies of Cr(CO)6 and (η6-C6H6) Cr(CO)2(CX) (X=O,S) complexes

Summary Quantum chemical calculations based on density functional theory have been performed on Cr(CO)₆, (⁶-C₆H₆)Cr(CO)₃ and (⁶-C₆H₆)Cr(CO)₂(CS) at the local and nonlocal level of theory using different functionals. Good agreement is obtained with experiment for both optimized geometries and metal-ligand binding energies. In particular, a comparison of metal-arene bond energies calculated for the (⁶-C₆H₆)Cr(CO)₃ and (⁶-C₆H₆)Cr(CO)₂(CS) complexes correlates well with kinetic data demonstrating that substitution of one CO group by CS leads to an important labilizing effect of this bond, which may be primarily attributed to a larger -backbonding charge transfer to the CS ligand as compared with CO.     

Speciation Study of Trace Elements by Reversed Phase-High Performance Liquid Chromatography ( Ⅰ )——Simultaneous Determination of Cr( Ⅲ ) and Cr( Ⅵ )

Reported here is the Cr-speciation study by High Performance Liquid Chromatography (HPLC) using precolumn derivatization with ammonium pyrolidinyldithiocarbamate (APDC) and spectrophotometric detection. The rapid and sensitive method has been successfully applied to the analysis of environmental water. The chromatographic behavior of the two Cr-APDC chelates are illustrated with "Solvophobic Theory".     

Luminescence line narrowing in [(bispicam)Cr(III) (OH2)(SO4)Cr(III) (bispicam)] S2O6·3H2O (bispicam = N,N'-BIS(2-pyridilmethyl)amine): Evaluation of exchange parameters

The title compound was studied by low-temperature luminescence spectroscopy. At 1.5 K the luminescence lines could be narrowed by selective dye-laser excitation, and the exchange splittings of the ground state were accurately determined. The splittings can be accounted for by a Heisenberg exchange operator supplemented by a biquadratic term.     

Reactions of (η6-diphenylacetylene) chromiumtricarbonyl complexes with polynuclear carbonyls I. Synthesis of Cr(CO)3(η6-diphenylacetylene) complex and its reaction with Co2(CO)8. Crystal and molecular structure of Cr(CO)3(η6:η2-diphenylacetylene)Co2(CO)6

The reaction of Cr(CO)₃(NH₃)₃ with diphenylacetylene affords as a main product the complex with Cr(CO)₃ moiety bound to a phenyl ring of diphenylacetylene; Cr(CO)₃(η⁶-PhC₂Ph) (I). Complex I readily reacts with Co₂(CO)₈ yielding the mixed metal complex Cr(CO)₃(η⁶:η²-PhC₂Ph)Co₂(CO)₆ (II). The reaction proceeds with retention of the Cr(CO)₃ (η⁶-arene) structural unit, the Co₂(CO)₆ fragment being bound to the triple bond of diphenylacetylene in μ₂,η²-mode. The structure of II was determined by single crystal X-ray analysis. The complex crystallizes in space group P2₁/c with unit cell parameters a 8.666(3) Å, b 18.046(3) Å, c 15.155(6) Å. β 97.57(3)°, V 2349(2) ų, Z = 4, D_x = 1.70 g/cm³. The structure was solved by direct methods and refined by full-matrix least-squares technique to R and R_w values of 0.032 and 0.034, respectively, for 3655 observed reflections. The data obtained show that two structural units in II, Cr(CO)₃(η⁶-Ph-) and Co₂(CO)₆(μ₂,η²-CC), are distorted due to steric repulsion between these metal carbonyl moieties. The Cr(CO)₃ fragment is shifted from the centre of the phenyl ring and slightly tilted with respect to the phenyl ring plane. The Co₂C₂ tetrahedron in the Co₂(CO)₆(μ₂,η²-CC) moiety is distorted in such a way that two of the four Co_iC_j bonds are elongated.     

Preparation and Identification of a New [Cr2(NTA)2(μ-OH2)]·2H2O Complex

[Cr₂(NTA)₂(μ-OH₂)]·2H₂O is prepared by heating nitrilotriacetic acid (H₃NTA) with an aqueous suspension of freshly precipitated Cr₂O₃·nH₂O. Elemental analysis, IR spectra, UV/vis spectra, X-ray diffraction, thermogravimetric analysis, mass spectra and magnetic susceptibility measurements suggest the existence of a Cr-Cr bond. One of the three water molecules acts as a bridging ligand (μ-H₂O) while the other two are waters of crystallization.     

Adsorption and Structural Properties of Montmorillonite Pillared by Cr(III) and Cr(III)–Cu(II) Hydroxocomplexes

The sorption and structural parameters and thermal stability of montmorillonite pillared by Cr(III) polyhydroxocomplexes and heteronuclear Cr(III)–Cu(II) polyhydroxocomplexes were investigated. It was shown that the introduction of intercalating Cr(III) and Cr(III)–Cu(II) agents into the montmorillonite increased the value of the first basal reflection (d ₀₀₁) up to 1.85 nm in the first case and up to 1.98 nm, in the second. The dependence of the values of d ₀₀₁and specific surface area on the OH^–/Cr³⁺ratio was found, which is retained during the calcination of the samples up to 500–800°C. The sorption ability of the prepared samples with respect to acetone, ethanol, benzene, toluene, and water was investigated.     

Co(III) and Cr(III) complexes of diphosphadithia ligands and the crystal structure of [CoCl2(L3)]PF6·CH2Cl2 (L3=Ph2P(CH2)2S(o-C6H4)S(CH2)2PPh2)

[CrX₃(thf)₃] (X=Cl or Br) reacts with L (L=L¹–L³ or Ph₂[14]aneP₂S₂) (L¹=Ph₂P(CH₂)₂S(CH₂)₂S(CH₂)₂PPh₂, L²=Ph₂P(CH₂)₂S(CH₂)₃S(CH₂)₂PPh₂, L³=Ph₂P(CH₂)₂S(o-C₆H₄)S(CH₂)₂PPh₂, Ph₂[14]aneP₂S₂=4,8-diphenyl-1,11-dithia-4,8-diphosphacyclotetradecane) and TlPF₆ in MeNO₂ solution to yield the distorted octahedral complexes [CrX₂(L)]PF₆ as green coloured solids in high yield. UV/visible spectroscopy suggests that these are cis-dihalo species and they have also been characterised by IR spectroscopy, electrospray mass spectrometry and microanalyses. The Co(III) analogues [CoX₂(L)]⁺ are readily prepared in a two-stage reaction, involving treatment of CoX₂·6H₂O with L (L=L¹–L³) and NH₄PF₆ in EtOH solution to give a green/brown solid, followed by halogen oxidation of this product in CH₂Cl₂ solution using X₂/CCl₄, to give the final products as brown coloured solids. A mixture of PF₆⁻ and [CoX₄]²⁻ anions are present in the final Co(III) compounds in varying ratios. Crystal structures of [CoCl₂(L²)]₂[CoCl₄]·4H₂O and [CoCl₂(L³)]PF₆·CH₂Cl₂ confirm tetradentate P₂S₂ coordination of L in each case, with mutually cis halogens completing the distorted octahedral geometry. In both cases the complex cation adopts the cis-α form in the solid state and this is also consistent with the solution ³¹P{¹H} NMR spectroscopic data. ⁵⁹Co NMR spectroscopy reveals a very broad single resonance at ≈3200 ppm for these species.     

Improvement on Simultaneous Determination of Cr(III) and Cr(VI) by Capillary Electrophoresis and Chemiluminescence Detection

Chromiumexistsindifferentoxidationstatesingroundwater,industrialwastewater,seawater,andsoilofourenvironment1,2.Chromium(III)isanessentialtraceelementforhumans,requiredforthemaintenanceofnormalglucose,cholesterol,andfattyacidmetabolism.Ontheotherhand,watersolublechromium(VI),intheformCr2O72-orCrO42-,ishighlyirritatingandtoxictohumansandanimals3.Itsacutetoxiceffectsincludeanimmediatecardiovascularshockandlatereffectsonkidney,liver,andblood-formingorgans.Therefore,itisnecessaryforriskassessme…     

Crystal structure and magnetic properties of a thiocyanato-bridged dinuclear Cr(III)Cu(II) complex [(HL)Cu(SCN)Cr(NCS)3(NH3)2]·DMF

The complex [(HL)Cu(SCN)Cr(NCS)₃(NH₃)₂]·DMF [H₂L=3,3′-trimethylenedinitrilobis(2-butanoneoxime), DMF=N,N′-dimethylformamide] has been synthesized and the structure determined by single-crystal X-ray diffraction. The structure consists of a dinuclear thiocyanato-bridged Cr(III)Cu(II) unit and a DMF molecule as crystal solvate. The chromium ion is six-coordinated with two NH₃ molecules in axial positions and four nitrogen atoms, from four NCS⁻, in equatorial positions. One of the NCS⁻ bridges the Cr and Cu ions, the S atom of which occupies the apex of the square-pyramidal coordination at Cu with the tetradentate HL ligand in the basal site. Cryomagnetic measurement revealed a weak antiferromagnetic coupling between the heterometal ions with J=−0.63 cm⁻¹ based on the spin Hamiltonian H=−2JS₁S₂.     

Thermal properties of potassium bis(oxalato)diaquochromates(III) in solid state. Trans–cis isomerization of the [Cr(C2O4)2(OH2)2]? complex ion in aqueous solutions

The thermal decomposition of trans-K[Cr(C₂O₄)₂(OH₂)₂]·3H₂O and cis-K[Cr(C₂O₄)₂(OH₂)₂] has been studied using the TG–MS technique. The measurements were carried out in an argon atmosphere over the temperature range of 293–873 K. The influence of the complex structures and configurational geometry on the stability of the transition products and the pathways of thermal transformations has been discussed. Furthermore, the kinetics of the isomerization reactions of the [Cr(C₂O₄)₂(OH₂)₂]⁻ complex ion catalyzed by five different metal ions: Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ have been studied. The isomerization reactions were studied in aqueous solution at five various temperatures (283–303 K), at constant concentration of metal ions (C = 0.1 M) and the constant ionic strength of solution (Na⁺, NO₃ ⁻) I = 2.4 M. The rates of the isomerization reaction were determined spectrophotometrically by monitoring of absorbance changes at 410 nm.     

Triclinic Structure of Birefringent Crystals of K(Al0.95Cr0.05)(SO4)2⋅12H2O

The crystal structure of alum K(Al_0.95Cr_0.05)(SO₄)₂12H₂O possessing anomalous birefringence was refined in space groups Pa3 and P1 (a = b = c = 12.165(2) , R = 0.0587). The distortions of cubic symmetry are attributed to the peculiarities of the orientational disorder in the distribution of SO₄ tetrahedra and to the different degrees of distortion of the aluminum octahedra.